The baryonic component of the universe post recombination was dominated by neutral hydrogen, which clumped into high density regions leading to the formation of first luminous sources in the universe. The emission from these first sources of radiation, ionized the neutral hydrogen in the intervening medium leading to an important phase transition of the universe called the Epoch of Reionization (EoR) [1]}, [2]}. The epoch is characterized by the appearance of ionized regions around these luminous sources, which gradually grow in size and merge until the entire universe is ionized [3]}. Therefore, studying the growth and topology of these ionized regions can help infer important properties of these first luminous sources. One promising observational probe of the EoR is the brightness temperature of the redshifted 21cm transition from neutral hydrogen atoms. The 21cm wavelength redshifts to the range of frequencies accessible by future radio telescopes and would serve as a direct probe of EoR [4]}. Statistically it is detected in terms of the sky averaged global signal or in terms of the power spectrum of the brightness temperature fluctuations. The global signal was recently claimed to have been detected by the EDGES experiment [5]} while the detection of the 21cm power spectrum is being aimed at by various ongoing interferometeric experiments such as Murchison Widefield Array (MWA), Low-Frequency Array (LOFAR), Giant Metrewave Radio Telescope (GMRT) and Precision Array for Probing the Epoch of Reionization (PAPER)  [6]}, [7]}, [8]}, [9]}. The upper limit on the dimensionless 21-cm power spectrum is \(\Delta ^2_{21} < (73)^2 \mathrm {mK}^2\)  at \(k=0.075 \mathrm {h~ c~ Mpc}^{-1}\)  as found by LOFAR at a redshift of \(z \simeq 9.1\)  [10]}.
